Rare earth metals and rare earth metal alloys have found use in ferrous metallurgy, particularly in the treatment of steel, where they accomplish deoxidation, desulfurization and modification of inclusions in steel. Treatment with rare earth metals and rare earth metal alloys results in increased hardness and impact strength and improved ductility and weldability of steel.
There is a present need for substantial quantities of high strength, low alloy (HSLA) steels. HSLA steels are used to form line pipe and in automotive applications, uses which place stringent controls on transverse impact toughness and formability of the steel.
It is well known that manganese sulfide inclusions form during the production of HSLA steels and that these inclusions play a detrimental role in reducing the transverse properties of rolled HSLA steel. That is, the inclusions, which are somewhat plastic in nature, elongate or string out during rolling producing areas of reduced strength (anisotropy) where manganese sulfide stringers form. The anisotropic properties are undesirable, of course, since line pipe or other articles made from HSLA steel may fail during use precisely in the areas of reduced strength.
Various agents, including rare earth metals, misch metal and rare earth metal alloys have been used to treat HSLA steels in an attempt to modify both the chemistry and shape of manganese sulfide inclusions and to aid in deoxidation and desulfurization of the steel. It is an object of this invention to provide improved rare earth metal silicide alloys useful for treatment of HSLA steels. A futher object of the invention is to provide a method for producing improved rare earth metal silicide alloys.